OUTLINE: Patients receive cytoreductive chemotherapy comprising busulfan IV over 2 hours every 6 hours for a total of 16 doses on days -8 to -5 and melphalan IV over 30 minutes on days -4 to -2. Patients undergo T-cell replete allogeneic bone marrow transplantation on day 0. For graft-versus-host disease prophylaxis, patients receive tacrolimus IV continuously or every 12 hours beginning on day -1 and continuing for 50 days to 6 months followed by a taper. Once oral medications are tolerated, patients switch to oral tacrolimus every 12 hours. Patients also receive methotrexate IV on days 1, 3, 6, and 11.